The present invention relates to a burner for supplying liquid fuel and air to a furnace and, more particularly, to a burner for supplying coal slurry fuel and air to a furnace.
One type of burner commonly utilized on industrial and certain utility furnaces firing liquid fuel, such as oil, is known as a round burner. In such a burner, a fuel supply pipe is disposed coaxially within an outer air supply conduit which comprises the outer housing of the burner. The fuel supply pipe opens into the furnace for spraying the liquid fuel into the furnace. One or more annular flow passages are defined coaxially about the fuel supply plate through which combustion air is passed into the furnace so as to annularly surround the liquid fuel sprayed into the furnace. One particular embodiment of this type of burner is disclosed is U.S. Pat. No. 3,743,471.
In recent years, interest has generated in the utilization of coal as a replacement fuel for more costly and less available fuel oil. One scenario for using coal as a replacement fuel for oil comprises burning the coal as a liquid by forming a mixture of coal and water which has the properties of a liquid slurry. However, experience has shown that coal-water mixtures, although liquid slurries, cannot be directly substituted for fuel oil on typical industrial and utility furnaces. Combustion characteristics of coal-water mixtures are not the same as the combustion characteristics of typical fuel oil. Additionally, the combustion characteristics of a coal-water mixture depend directly upon the coal being utilized in the mixture. Therefore, as coals vary substantially in their combustion characteristics, the burning equipment utilized on a furnace firing coal-water slurry must be capable of handling liquid fuels having a wide range of combustion characteristics as one cannot be assured of always having available a coal-water slurry made from a particular coal.
Accordingly, it is an object of the present invention to provide a burner for supplying a coal-water mixture and combustion air to a furnace which is uniquely designed to be capable of adjustment to handle a wide range of coal-water mixtures.
Additionally, it is an object of the present invention to provide such a coal-water slurry burner which is capable of operating with a high turndown.